Update or remove `sig/amqp-client.rbs`

[dentarg]

What can sig/amqp-client.rbs be used for? Do we need it in the repo? Currently I think it is a bit outdated (after running typeprof lib/amqp-client.rb > sig/amqp-client.rbs there's quite the diff)

amqp-client.rb/sig/amqp-client.rbs

Lines 1 to 4 in 9b06622

	# TypeProf 0.15.3
	# Classes
	module AMQP

[carlhoerberg]

fixed